For use in compact disc players for reproducing digital audio signals from compact discs wherein the signals are optically recorded, Examined Japanese Patent Publication SHO 60-80159, for example, discloses a loading device for transporting the disc to a signal reproducing position inside the player. The disclosed loading device comprises a tray having a disc support portion, retractably provided at the front panel of the player body and horizontally reciprocatingly movable by the power of a motor. The tray has a lifter for slightly lifting the disc during the transport thereof, while disc clamper is provided inside the player above a turntable for holding the disc in pressing contact with the turntable. After the disc supported on the tray by the lifter has been transported into the player, the disc clamper lowers with the retraction of the lifter into the tray, and the disc on the tray is lowered onto the turntable and held in pressing contact with the turntable.
The disc player described above requires, in addition to a mechanism for reciprocatingly driving the tray, a mechanism for driving the disc clamper upward and downward and a mechanism for operating the lifter. The player therefore has the problem of being large-sized and necessitates an increased number of parts.
On the other hand, Unexamined Japanese Patent Publication SHO 61-145758 discloses a disc player which comprises, as seen in FIG. 26, a subchassis 161 pivotally movably supported by a shaft 162 on a main chassis 160 and having mounted thereon a turntable 163, pickup 164, pickup transport mechanism 165, etc. A disc clamper 166 is mounted on the main chassis 160 rotatably but immovably upward or downward. When a tray 168 is pushed into the body of the player, the subchassis 161 is moved upward by the operation of a chassis drive mechanism 167. With this movement, the turntable 163 on the sub-chassis 161 lifts a disc off the tray 168 and presses the disc against the clamper 164, whereby the disc is completely loaded. Accordingly, the disc can be lifted and lowered and the turntable is caused to effect a clamping action by a mechanism which is merely adapted to pivotally move the subchassis.
However, the disc player is cumbersome to use since the tray 168 must be reciprocatingly moved manually. The tray may be made automatically movable by providing a known tray drive mechanism which is operable by a motor, whereas the motor, if additionally provided, makes the player larger and heavier and needs a motor control circuit, which makes the circuit of the player complex in construction.
With disc players, an optical pickup is moved along a radial line of the disc which is rotating at a hight speed for the pickup to trace tracks formed on the signal bearing surface thereof in the form of concentric circles or a spiral track thereon and thereby read signals. Unexamined Japanese Patent Publication SHO 62-62485, for example, discloses a mechanism for transporting the pickup.
The disclosed transport mechanism comprises a guide shaft for guiding the pickup for a linear motion thereof, a rack secured to the pickup immovably relative thereto, a pinion in mesh with the rack, and a feed motor for driving the pinion. The pickup is reciprocatingly movable by the operation of the feed motor.
With the above pickup transport mechanism, the pickup is mounted on the guide shaft without any backlash so as to be movable straight accurately, with the rack secured to the pickup immovably relative thereto, so that the pitch line of the rack must be parallel to the direction of movement of the pickup with high precision. .If the parallelism is low, the distance between the rack and the pinion varies with the travel of the pickup, impairing the proper meshing engagement therebetween and giving rise to the problem that the power of the motor will not be transmitted to the pickup smoothly, for example, owing to objectionable meshing of the rack with the pinion.
With disc players adapted for a multiplicity of functions in recent years, disc players have been proposed wherein two discs can be loaded at the same time for a single pickup to read signals therefrom in a desired order (as disclosed, for example, in Unexamined Japanese Patent Publication SHO 57-195368). With this player, two discs are arranged side by side on a plane within the player, and the pickup is reciprocatingly transported along a path extending over the two discs.
In the case where the foregoing drive mechanism comprising a rack and a pinion is employed for transportion the pickup of such a disc player, the above-mentioned problem arising from the poor parallelism between the rack and the direction of pickup movement becomes more pronounced because the distance of movement of the pickup is more than twice the corresponding distance in conventional common disc players, necessitating a rack with more than twice the conventional length.
Although the disc player disclosed in the Publication SHO 57-195368 is adapted to reproduce signals successively from the two discs loaded therein, the player is not of the front loading type and therefore has the drawback that discs are not loadable conveniently.